1. Field of the Invention
The present invention relates to a blower fan of an inner-rotor type.
2. Description of the Related Art
In recent years, electronic devices, such as notebook personal computers and tablet personal computers, have been becoming thinner and thinner. In addition, such electronic devices have been becoming more and more sophisticated in functionality, causing a considerable increase in generation of heat in the electronic devices. Inside such slim electronic devices, a large number of electronic components are arranged, and a space occupied by an air is not large. Therefore, even in the case where components inside such an electronic devices do not generate much heat, a temperature inside the electronic device may quickly increase. Accordingly, it is necessary to cool an interior of the electronic device, and a blower fan is arranged inside the electronic device to cool the interior of the electronic device.
In a case of an electronic device which is not of a slim type, there is a large space in which electronic components are not arranged, and such an electronic device does not impose a heavy load on a blower fan installed therein. That is, an interior of the case is in a low static pressure environment. Therefore, even a blower fan which is inferior in a static pressure characteristic is able to send an air in a sufficient manner.
In contrast, in an electronic device of the slim type, only a small amount of air exists in a space in which no electronic components are arranged, and the electronic device of the slim type imposes a heavy load on a blower fan installed therein. That is, an interior of a case of the electronic device of the slim type is in a high static pressure environment. Therefore, the blower fan which is inferior in the static pressure characteristic is not able to send an air in a sufficient manner.
In this connection, JP-A 2009-203837 discloses the structure of a centrifugal fan in which an air outlet 21 is defined in a side wall of a casing 2 and is located in a direction in which an air is sent by an impeller 1, and in which air inlets 24 and 25 are defined in the side wall of the casing 2.
However, regarding the centrifugal fan disclosed in JP-A 2009-203837, a space from which an air can be sucked into the casing is required radially outside the side wall of the casing in a case of an electronic device in which the centrifugal fan is installed. It is not easy to provide a planar space in the case of the electronic device of the slim type, and since a large number of electronic components are arranged in such a planar space, it may be impossible to provide a sufficient space in the vicinity of the side wall of the casing of the centrifugal fan. In that case, installation of the centrifugal fan disclosed in JP-A 2009-203837 can neither achieve a sufficient air-blowing performance nor secure a sufficient amount of air to be discharged.